Void

Definition - What does Void mean?

A void is an area that has no ballast, cargo or fluids like water or fuel. At times, these are known as dry spaces. However, this could be misleading since voids usually contain fluids coming from leaks, new buildings or other sources.

Voids without exposure to air may have high amounts of retained solvent. The best examples of this are pipe ducts and stools. High levels of solvent may sustain coating in a comparatively soft state that does not defend against the corrosion process.

Corrosionpedia explains Void

Voids result from the buildup of vapor cavities within a liquid and serve as a consequence of the forces acting on the liquid. This usually takes place when liquids are faced with rapid pressure changes when there is a comparatively low pressure in the liquid itself. When voids are subjected to higher levels of pressure, they can implode and produce severe shock waves.

Voids are one of the main causes of corrosion or wear in most engineering contexts. Voids, especially the collapsing type that implode close to metal particles, can result in cyclic stress that can be brought about by repeated implosion. This leads to metal surface fatigue or wear, particularly cavitation. This typically occurs in bends and pump impellers, where there is a rapid change in liquid direction.

Voids are common in inertial cavitation where rapid collapse within a liquid gives off shock waves. This phenomenon can occur in parts such as:

Pumps

Control valves

Impellers

Propellers

In the process of non-inertial cavitation, the void within a fluid is pushed to oscillate in shape or size because of certain types of energy input like in an acoustic field. This type of void can be seen in ultrasonic cleaning baths as well as in propellers and pumps.

Shock waves that are formed due to collapsing voids are powerful enough to lead to tremendous damage to movable parts, making it an undesirable phenomenon. Hence, it is avoided in terms of designing propellers, turbines and other parts. Yet there are times when voids are useful and do not cause wear, such as in cases of supercavitation when the void tends to collapse away from the equipment or machinery.